page_title: LED circuit
section_title: LED arrays
hierarchical_section_title: LED circuit / LED arrays
caption_attribution_description: 中文（繁體）‎: 當總LED順向偏壓高於電源電壓時的線路接法。
context_page_description: In electronics, an LED circuit or LED driver is an electrical circuit used to power a light-emitting diode. The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED. The voltage drop across an LED is approximately constant over a wide range of operating current; therefore, a small increase in applied voltage greatly increases the current. Very simple circuits are used for low-power indicator LEDs. More complex, current source circuits are required when driving high-power LEDs for illumination to achieve correct current regulation.
context_section_description: Strings of multiple LEDs are normally connected in series. In one configuration, the source voltage must be greater than or equal to the sum of the individual LED voltages; typically the LED voltages add up to around two-thirds of the supply voltage. A single current-limiting resistor may be used for each string.
  Parallel operation is also possible but can be more problematic. Parallel LEDs must have closely matched forward voltages (Vf) in order to have similar branch currents and, therefore, similar light output. Variations in the manufacturing process can make it difficult to obtain satisfactory operation when connecting some types of LEDs in parallel.
caption: Schematic of LEDs in parallel
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